Filarial nematode infections

Table 2.1. Filarial nematodes infected with intracellular bacteria. The method of detection is shown. Neither electron microscopy nor the immuno-histochemical staining techniques used are to be regarded as Wolbachia specific (see note). Positive identification of intracellular bacteria as Wolbachia is shown only where PCR amplified products of rRNA or ftsZ genes have been sequenced. ...

Immunological Defects Associated with Human Filarial Nematode Infection a Role for PC ... 

Harnett, W., Bradley, J.E. and Garate, T. (1998b) Molecular and immunodiagnosis of human filarial nematode infections. Parasitology 117 (Supplement), S59-71. 

Ivermectin (Mectizan, Stromectol) is the primary treatment for filarial nematode infections (onchocerciasis) that invade ocular tissues and cause loss of vision (river blindness). Ivermectin may also be used in filarial infections in other tissues (lymphatics, skin). This drug is a secondary agent for treating intestinal nematodes such as strongyloidosis. 

Exhaustive surveys have not been carried out to determine the prevalence of infection within a single species of filarial nematode. However, infection was found in all eight specimens of D. immitis collected from worldwide locations, indicating that infection prevalence is likely to be close to 100% (Sironi et al., 1995). Sequences of Wolbachia ftsZ genes from... 

Bazzocchi, C., Ceciliani, F., McCall, J.W., Ricci, I., Genchi, C. and Bandi, C. (2000b) Antigenic role of the endosymbionts of filarial nematodes IgG response against the Wolbachia surface protein in cats infected with Dirofilaria immitis. Proceedings of the Royal Society of London B (in press). 

Wu, Y., Adam, R, Williams, S.A. and Bianco, A.E. (1996) Chitinase genes expressed by infective larvae of the filarial nematodes, Acanthocheihnema viteae and Onchocerca volvulus. Molecular and Biochemical Parasitology 75, 207—219. 

Another interesting observation is that several species of filarial nematodes have been shown to express chitinase (Fuhrman, 1995). Indeed the chitinase of A. viteae infective stage larvae (L3) is the main target of the protective humoral immune response when jirds are vaccinated with irradiated attenuated L3s (Adam et al., 1996 see also Chapter 10). It remains to be established whether there is an interaction between the parasite s oligo-chitin A-glycans and chitinase and whether such an interaction has a role to play in parasite-host interaction. 

Maizels, R.M., Burke, L. and Denham, D.A. (1987c) Phosphorylcholine-bearing antigens in filarial nematode parasites analysis of somatic extracts, in-vitro secretions and infection sera from Brugia malayi and B. pahangi. Parasite Immunology 9, 49-66. 

PC can also be detected on the surface of L3 infective stages of filarial nematodes and there is some indication from studies on rodent... 

Parasitic helminths, such as Ascaris lumbricoides, Trichuris trichiura, hookworms, schistosomes and filarial nematodes are highly prevalent in tropical and subtropical areas of the world [1]. These infections often overlap and affect more than 1 billion... 

Goodridge HS, Wilson EH, Harnett W, Campbell CC, Harnett MM, Liew FY (2001) Modulation of macrophage cytokine production by ES-62, a secreted product of the filarial nematode Acanthocheilonemaviteae. J Immunol 167 940-945 Gounaris K (2002) Nucleotidase cascades are catalyzed by secreted proteins of the parasitic nematode Trichinella spiralis. Infect Immun 70 4917-4924... 

Houston KM, Wilson EH, Eyres L, Brombacher E, Harnett MM, Alexander J, Harnett W (2000) Presence of phosphorylcholine on a filarial nematode protein influences immunoglobulin G subclass response to the molecule by an interleukin-10-dependent mechanism. Infect Immun... 

Mebendazole exerts its effects slowly (3 days), and effectiveness of treatment depends on the degree of infection or resistance of the parasites to treatment. Phenytoin or car-bamazepine reduce the plasma level of mebendazole. The major nematode parasites of humans include soil-transmitted helminths (STHs sometimes referred to as geohelminths ) and the filarial nematodes. 

The major nematode parasites of humans include the soil-transmitted helminths (STHs) and the filarial nematodes. The STH infections, which include ascariasis, trichuriasis, and hookworm infection, are among the most prevalent infections in developing countries. Eradication programs use schools to administer broad-spectrum anthelmintics on a periodic and frequent basis. The most widely used agents for reducing morbidity are the benzimidazole anthelmintics (BZAs), either albendazole (albenza and zentel) or mebendazole (VEEtMOX) (see Table 41-1). 

Gomez-Escobar N, Gregory WF, Maizels RM 2000 Identification of Bm-tgh-2, a filarial nematode homolog of C. elegans daf-7 and human TGF-P, expressed in microfilarial and adult stages of Brugia malayi. Infect Immun 68 6402-6410... 

Onchocerciasis is a blinding disease caused by infection with the filarial nematode parasite. Onchocerca volvulus. This disease is endemic in many parts of the tropics, particularly... 

Fig. 9.1. Transmission electron micrographs of parasitic nematode cuticles in transverse section. The structurally distinct layers and the underlying hypodermal syncytia are indicated. Nematodes depicted are the infective larval stage of the canid parasite Toxocara canis and the fourth larval stage of the human filarial parasite Brugia malayi.

The filarial worms differ from other nematodes in that they are threadlike and are found in blood and tissue. The infective larvae enter following the bite of an infected arthropod (fly or mosquito). They then enter the lymphatics and lymph nodes. Fever, lymphangitis, and lymphadenitis are associated with the early stage of the disease. Chronic infections may be characterized by elephantiasis as a result of lymphatic obstruction. Some species of filarial worms migrate in the subcutaneous tissues and produce nodules and blindness (onchocerciasis). 

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